1. Field of the Invention
The present invention relates to a scanning-type image display apparatus which displays an image by performing two-dimensional scanning with a light beam modulated on the basis of image information and emitted from a light source unit.
2. Description of the Related Art
Various two-dimensional scanning-type image display apparatuses, which display a two-dimensional image by causing a scanning unit (such as a micromechanical mirror) to two-dimensionally scan a surface to be scanned with laser light, modulated on the basis of image information, and by making use of a residual-image effect of a light spot formed on the scanning surface have been discussed (refer to Japanese Patent Laid-Open No. 2004-264670 (no corresponding foreign documents) and U.S. Pat. No. 5,489,950).
Japanese Patent Laid-Open No. 2004-264670 (hereunder referred to as “Patent Document 1”) discusses an image display apparatus which displays an image by performing two-dimensional deflection scanning on a scanning surface with a light beam that is deflected horizontally and vertically by two deflecting units (scanning units) comprising mirrors that are subjected to resonant driving.
In Patent Document 1, a high-definition image is displayed by using as a scanning unit, resonant deflectors which can deflect light at an equivalently high speed. In addition, Patent Document 1 discusses a method for controlling driving of the resonant deflectors with high precision.
U.S. Pat. No. 5,489,950 (hereunder referred to as “Patent Document 2”) discusses a display apparatus which projects as a two-dimensional image a one-dimensional image subjected to deflection scanning by a deflecting mirror.
In Patent Document 2, a displacement angle of the deflecting mirror, which serves as a scanning unit and vibrates at a constant angle and at a constant period, is detected by a detector mounted to the deflecting mirror, and a scanning synchronization timing signal is generated on the basis of a signal obtained at the detector.
In such scanning-type image display apparatuses, a light beam can no longer properly scan the scanning surface due to a failure of the scanning unit. In such a case, it can be useful to stop driving the light source unit which emits a light beam modulated on the basis of image information.
In particular, when the light source unit is driven by, for example, a battery, in order to reduce the chance of battery exhaustion, it can be useful to perform an appropriate operation on the light source unit when a failure occurs in the scanning unit.
Patent Documents 1 and 2 do not discuss anything about, for example, what can be done when a failure occurs in the scanning unit or the light source unit.